High resolution display panel with emissive organic layers emitting light of different colors

ABSTRACT

An arrangement for a high resolution active matrix display includes organic emissive layers of distinct colors each deposited across continuous regions so as to include more than one pixel emissive region. Color filters are situated to partially block light from at least some of the emissive regions such that primary additive colors are transmitted from distinct subsets of pixels. The emissive layers may be deposited in alternating parallel stripes along rows or columns of the display, or may be oriented perpendicularly with respect to one another such that the emissive layers overlap in the emissive regions of at least some pixels. In some examples, red, green, and blue of pixels are arranged in regular patterns across the display and with the emissive regions for the blue pixels forming a relatively larger area of the display than either the red or green pixels.

FIELD OF THE INVENTION

The present disclosure generally relates to flat panel displays formedby controllably depositing materials on a substrate and systems andmethods for manufacturing such displays, and, more particularly, toorganic light emitting diode displays where light emissive layers aredeposited on a display substrate through a shadow mask.

BACKGROUND

Displays can be created from an array of organic light emitting devices(“OLEDs”) each controlled by individual circuits (i.e., pixel circuits)having transistors for selectively controlling the circuits to beprogrammed with display information and to emit light according to thedisplay information. Thin film transistors (“TFTs”) fabricated on asubstrate can be incorporated into such pixel circuits.

Generally, such pixel circuits include a drive transistor that conveyscurrent through an organic emissive layer. Light is generated within theemissive layer due to recombination of holes and electrons passingthrough the layer in opposite directions. Accordingly, the intensity ofemitted light is controlled by the amount of current flowing through theemissive layer, and the color of the emitted light is determined by theenergy transitions allowed during recombination events, which is afunction of the particular organic material selected as the emissivelayer. Furthermore, current through the emissive layer is controlled bythe voltage(s) applied to the drive transistor, which adjusts theconductivity of the drive transistor's channel region to control thecurrent levels through the emissive layers (and the light emission).

Color displays are created by arranging a display with roughly a thirdof pixels emitting red light, a third emitting green light, and a thirdemitting blue light, with each group of three pixels forming an RGBpixel group composed of three sub-pixels that are independentlyprogrammed. Color content is displayed by programming each RGB pixelgroup to emit light according to a desired color for each positioncreated by adding the RGB content together. Providing RGB pixels can beachieved by using emissive layers that generate light in red, green, andblue, respectively and patterning the appropriate emissive layers in theemissive regions of desired pixel circuits to create a desired RGBpattern.

Manufacturing such displays thus requires precisely patterning therespective emissive layers such that the appropriate emissive materialis positioned in the proper emission region for each pixel. Shadow masksformed of thin metal are employed to screen regions where the emissivematerial is not desired while the emissive material is deposited on thedisplay through the shadow mask. A shadow mask thus has a pattern ofholes corresponding to the emission regions of all the red pixels and isaligned such that the holes match with the red pixels and the redemissive material is deposited. The shadow mask can then be moved (oranother shadow mask positioned) such that holes align with the greenpixels, and the green emissive material is deposited, etc. At very highpixel resolution (i.e., small pixel size) the holes in the shadow maskmust become very small and the accuracy of the procedure suffers fromnon-uniformities in the emissive layers and difficulties in accuratelyaligning small holes.

In other examples, color displays can be formed from white emissivelayers that are filtered to allow particular colors to be transmitted.That is, emissive layers that generate white light (which is itself acombination of red, green, and blue) can be provided in the emissivelayers of all pixels. Color filters are arranged on the displaysubstrate associated with particular pixels such that red, green, andblue light are transmitted from the display according to a desired RGBpattern. Filtering each color wastes a lot of power as a lot ofgenerated light energy is simply filtered out with only a fraction beingtransmitted to contribute to the displayed color content.

SUMMARY

Arrangements and layouts are disclosed herein for multi-color pixelgroups suitable for being patterned across a color display at a highpixel density. Some arrangements include organic emissive layersemitting distinct colors each deposited across continuous regions of adisplay panel so as to include more than one pixel emissive region.Color filters are situated to partially block light from at least someof the emissive regions such that primary additive colors aretransmitted from distinct subsets of pixels on the display panel. Somearrangements provide for emissive layers deposited in alternatingparallel stripes along rows or columns of the display. Some arrangementsprovide for emissive layers to be oriented perpendicularly with respectto one another such that the emissive layers overlap in a stackedconfiguration in the emissive regions of at least some pixels. In someexamples, red, green, and blue of pixels are arranged in regularpatterns across the display and with the emissive regions for the bluepixels forming a relatively larger area of the display than either thered or green pixels.

Aspects of the present disclosure provide a high resolution displaypanel including a display substrate, first and second substantiallycontinuous emissive organic layer, and one or more first color filters.The display substrate includes a plurality of driving circuits eachincluding a drive transistor coupled to an electrode such that thesubstrate includes a plurality of electrodes each coupled to arespective drive transistor. The first substantially continuous emissiveorganic layer is deposited in a first area of the display panelincluding at least two of the plurality of electrodes. The firstemissive organic layer is configured to emit light according to a firstcolor spectrum responsive to current being conveyed through the firstemissive organic layer. The second substantially continuous emissiveorganic layer is deposited in a second area of the display panelincluding at least two of the plurality of electrodes. The secondemissive organic layer configured to emit light according to a secondcolor spectrum responsive to current being conveyed through the secondemissive organic layer. The first color filters are situated topartially block light emitted from at least one of the first or thesecond emissive organic layers such that light transmitted through theone or more first color filters is characterized by a color spectrum fora first fundamental color.

Aspects of the present disclosure provide a method of fabricating a highresolution display panel that includes a display substrate with aplurality of driving circuits conveying currents to a plurality ofelectrodes via drive transistors and an emission region receiving thecurrents from the plurality of electrodes. The method includesdepositing first and second substantially continuous emissive organiclayers, and situating one or more first color filters situated topartially block light emitted from at least one of the first or thesecond emissive organic layers. The first substantially continuousemissive organic layer is deposited with a substantially constantthickness in a first area of the display panel including at least two ofthe plurality of electrodes. The first emissive organic layer isconfigured to emit light according to a first color spectrum responsiveto current being conveyed through the first emissive organic layer. Thesecond substantially continuous emissive organic layer is deposited witha substantially constant thickness in a second area of the display panelincluding at least two of the plurality of electrodes. The secondemissive organic layer is configured to emit light according to a secondcolor spectrum responsive to current being conveyed through the secondemissive organic layer. The one or more one or more first color filtersare situated to such that light transmitted through the one or morefirst color filters is characterized by a color spectrum for a firstfundamental color.

Aspects of the present disclosure provide a high resolution displaysystem including a display substrate, a first multi-color pixel groupsituated on the display substrate, and a controller. The firstmulti-color pixel group includes a first pixel circuit, a second pixelcircuit, a first substantially continuous emissive layer, and a firstcolor filter. The first pixel circuit includes a first emission regionand a driving circuit having a drive transistor and a storage capacitorconfigured to convey current through the emission region via the drivetransistor according to a charge on the storage capacitor. The secondpixel circuit includes a second emission region and a driving circuithaving a drive transistor and a storage capacitor configured to conveycurrent through the emission region via the drive transistor accordingto a charge on the storage capacitor. The first substantially continuousemissive layer is deposited with a substantially constant thickness in afirst area including the first emission region and the second emissionregion. The first emissive layer is configured to emit light accordingto a first color spectrum responsive to current being conveyed throughthe first emissive layer. The first color filter is situated topartially block light emitted from the first emission region such thatlight of a first fundamental color is transmitted through the firstcolor filter. The controller is configured to program the drivingcircuits of the first and second pixel circuits according to programminginformation during a programming cycle such that the pixel circuits emitlight according to the programming information during a driving cyclefollowing the programming cycle.

The foregoing and additional aspects and embodiments of the presentinvention will be apparent to those of ordinary skill in the art in viewof the detailed description of various embodiments and/or aspects, whichis made with reference to the drawings, a brief description of which isprovided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1A is an exploded diagram of a display panel with a TFT backplanehaving an array of electrodes for driving current through one or moreorganic emissive layers and a pattern of color filters to partiallyblock light from the emissive layers.

FIG. 1B is a circuit diagram of a representative driving circuit in theTFT backplane for a pixel in an active matrix display including astorage capacitor and a drive transistor for conveying current throughthe emission region according to charge on the storage capacitor.

FIG. 1C is a side view of an emissive region for a single pixelincluding stacked emissive layers and a color filter.

FIG. 2A is a top view of a layout for an RGBW multi-color pixel groupformed with a substantially continuous strip of blue emissive materialon the blue and white terminals.

FIG. 2B is an aspect view of the RGBW multi-color pixel group layoutwith the strip of blue emissive material formed over a layer of orangeemissive material.

FIG. 2C is an aspect view of the RGBW multi-color pixel group layoutwith the layer of orange emissive material formed over the strip of blueemissive material.

FIG. 2D is a top view of an alternative configuration of the RGBWmulti-color pixel group with the red and green sub-pixels havingelongated emissive regions.

FIG. 2E is a top view of a layout for an RGB multi-color pixel groupincluding emissive layers arranged similarly to the layouts of FIGS. 2Aand 2D.

FIG. 3A is a top view of a layout for an RGB multi-color pixel groupformed from alternating strips of orange and blue emissive material andwith a blue sub-pixel enlarged relative to red and green sub-pixels.

FIG. 3B is a top view of a layout for an RGB multi-color pixel groupsimilar to the layout in FIG. 3A, but where the red and green sub-pixelshave elongated emissive regions.

FIG. 4A is another top view of a layout for RGB multi-color pixel groupsformed from alternating strips of orange and blue emissive materials andwith adjacent blue subpixels being associated with red and greensub-pixels in alternating upper and lower rows.

FIG. 4B is a top view of a layout for an RGB multi-color pixel groupsimilar to the layout of FIG. 4A, but where the blue subpixels in eachRGB multi-color pixel group have a larger area than either the red orgreen subpixels.

FIG. 4C is a top view of a layout for an RGB multi-color pixel groupsimilar to the layout of FIG. 4B but where adjacent multi-color pixelgroups share a common unitary blue subpixel.

FIG. 4D is a top view of a layout for an RGB multi-color pixel groupsimilar to the layout of FIG. 4B with the red and green sub-pixelshaving elongated emissive regions.

FIG. 5 is a top view of a layout for an RGB multi-color pixel groupformed from parallel strips of red and green emissive materialsoverlapped with perpendicularly aligned strips of blue emissivematerial.

FIG. 6A is a top view of a layout for RGB multi-color pixel groupsformed from parallel strips of red and green emissive materialsoverlapped with perpendicularly aligned strips of blue emissive materialwith blue sub-pixels enlarged relative to red and green sub-pixels.

FIG. 6B is an aspect view of the RGB multi-color pixel groups of FIG. 6Ashowing alignment of the layers of emissive material and color filterswith respect to a TFT backplane.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1A is an exploded diagram of a display panel 10 with a TFTbackplane 20 having an array of electrodes for driving current throughone or more organic emissive layers 40 and a pattern of color filters 60to partially block light 50 from the emissive layers 40. The TFTbackplane 20 can be formed on a substrate and include an array of pixelcircuits for receiving programming information and conveying drivingcurrents 30 through the emissive layers 40. Generally, the TFT backplane20 includes an array of electrodes (e.g., the electrodes 22r, 22g, 22b,etc.) arranged in rows and columns with each electrode being associatedwith a distinct pixel circuit for driving current through the emissivelayers 40 via its respective electrode.

Generally, the TFT backplane is an active matrix backplane and eachpixel circuit in the TFT backplane includes a drive transistor and astorage capacitor. The drive transistor is generally in series with itsrespective electrode such that currents driven through the drivetransistor are also conveyed through the corresponding portions of theemissive layers 40, via its respective electrode. The storage capacitoris generally situated to influence the conductance of the drivetransistor such that the current conveyed through the drive transistoris controlled by the charge on the storage capacitor. The charge on thestorage capacitor can be set (i.e., programmed) according to programminginformation conveyed to the pixel circuit via a data line driven by adata driver according to display information, such as, for example adigital video stream. Thus, in some embodiments, each pixel circuit canbe programmed according to display information during a programmingcycle, which charges the storage capacitor via voltage programming,current programming, or a combination thereof, and then driven to emitlight according to the programming information during an emission cyclefollowing the programming cycle. In some embodiments, the duration ofthe programming cycle corresponds to an interval during which the pixelcircuit is connected to a data line.

An exemplary pixel circuit 100 is provided in FIG. 1B, which isdiscussed further below. In an example implementation, the pixelcircuits in the TFT backplane 20 can be configured different from thepixel circuit 100 shown in FIG. 1B. The TFT backplane 20 can includeconnections to a data driver 132 and an address driver 134 to programand drive the pixel circuit 100 to convey the driving currents 30 to theemission layers 40 and thereby cause emitted light 50 to be transmittedthrough the color filter layer 60 such that the filtered light 70 istransmitted outward from the display system 10. As shown in theexemplary pixel circuit 100 of FIG. 1B, a controller 130 receivesdisplay data 138 and sends command signals to the address driver 134 andthe data driver 132 cause the pixel circuit 100 to be programmed anddriven according to the received display data 138. The controller 130can also adjust (“tune”) the programming and/or driving according toinformation stored in an associated memory 136. For example, the memory136 can include a lookup table to provide adjustment values for one ormore pixel circuits in the display panel including the pixel circuit 100to scale or otherwise adjust programming values to account fordegradation (e.g., aging) of the electrical components within the pixelcircuit 100. For example, the programming values can be adjusted toaccount for changes in threshold voltage of the driving transistor,changes in the turn on voltage of the light emitting device, and/orchanges in the current-voltage characteristics of the drivingtransistor. Additionally or alternatively, the memory 136 can storecoefficients for formulas (or lookup tables) characterizing an amount ofadjustment for each pixel circuit (or subsets thereof) based on theprogramming value provided, the operation history of the pixel circuit,one or more measurements of the pixel circuit (e.g., current values,light emission values, etc.), and/or the age (“operating hours”) of thedisplay.

Generally, the TFT backplane 20 includes a plurality of distinct pixelcircuits that can each be programmed according to programminginformation and driven to provide a driving current through an emissiveregion according to the programming information. The driving currentscan be conveyed via distinct driving terminals associated with eachpixel circuit. By programming the full panel of such pixel circuits, thedisplay panel 10 can be driven to display an image, and dynamicallyupdating the displayed content at a sufficiently high refresh ratecauses the display panel 10 to display video content. Furthermore, thedisplay panel 10 can display color content by situating pixels that emitparticular colors across the display panel. For example, the displaypanel 10 can be arranged with a regularly repeating pattern of red,green, and blue pixels such that a light can be generated from thedisplay panel according to a programmable combination of red, green, andblue light. Additionally or alternatively, the display panel 10 can alsobe arranged with pixels emitting white light, cyan light, magenta light,yellow light, orange light, etc. The exemplary arrangement ofcolor-specific pixels shown in FIG. 1A is described next in detail.

The TFT backplane 20 includes a first pixel group 22 and a second pixelgroup 24. Both the first pixel group 22 and the second pixel group 24include three distinct pixel circuits each having a distinct terminal.The first pixel group 22 includes a red terminal 22r, a green terminal22g, and a blue terminal 22b. The second pixel group 24 also includes ared terminal 24r, a green terminal 24g, and a blue terminal 24b. Drivingcurrents 30 are conveyed via the respective terminals 22r,g,b, 24r,g,b,etc. to the emissive layer 40. The emissive layer 40 is arranged withalternating elongated strips of substantially continuous blue emissivematerial 41, 48 and orange emissive material 45. Certain organicmaterials have molecular structures that provide an energy gap betweenthe highest occupied molecular orbital and the lowest unoccupiedmolecular orbital, and by injecting holes and free electrons to theorganic material, luminescent recombination events occur to emit lightwith characteristic energies near the energy gap. Accordingly,particular organic materials can be selected with electroluminescencespectra of varying colors, such as materials emitting blue light, orangelight, red light, etc. to generate the emitted light 50 with desiredcolor characteristics. In the display panel 10 shown in FIG. 1A, thestrips of blue emissive material 41, 48 emit blue light while the stripof orange emissive material 45 emits orange light.

The first strip of blue emissive material 41 is situated to overlap(“coat”) the blue terminals 22b, 24b from the first and second pixelgroups 22, 24. The first strip of blue emissive material 41 can bedeveloped over the blue terminals 22b, 24b by a deposition process usinga thin shadow mask with an elongated slit opening situated over an areaincluding the blue terminals 22b, 24b. Similarly, the strip of orangeemissive material 45 is situated to overlap (“coat”) the red and greenterminals 22r,g and 24r,g from the first and second pixel groups 22, 24,and can be developed by a deposition processing using a thin shadow maskhaving an elongated slit opening. Thus, the strips of emissive material41, 45 generally each extend continuously over an area of the displaypanel that includes more than one terminal of the TFT backplane 20.However, as previously described the emissivity of the emissive strips41, 45 (i.e., the luminance emitted light 50) is regulated by the amountof current flowing through the materials (and thus the amount oflight-emitting recombination events occurring within the materials).

The driving currents 30 flow through the emissive layers 40 primarilyvertically through the material along the shortest path between theterminals of the TFT backplane and corresponding terminals on theopposite side of the emissive layer 40, which may be, for example,transparent conductive terminals of indium tin oxide (ITO) or a similarmaterial providing a supply line voltage (e.g., Vdd or Vss). Inparticular, the emissive layers 40 are relatively resistive to currentflowing horizontally along the layers 40, rather than through the layers40, thus the driving currents 30 from each terminal in the TFT backplane20 generally flow through the layers 40 only in confined regionssituated over each terminal. In other words, the strips of emissivematerial 41, 45, 48 can be considered as an array of separatelyprogrammed emissive regions for each pixel circuit, even though thestrips 41, 45, 48 are arranged as continuous layers spanning multiplepixels. In the exemplary configuration of the display panel 10, thefirst strip of emissive blue material 41 includes a first area 42 and asecond area 43 each situated over a distinct terminal in the TFTbackplane 20. The first area 42 is situated to overlap the blue terminal22b in the first pixel group 22 and emit blue light according to thedriving current 30 from the blue terminal 22b. The second area 43 issimilarly situated to overlap the blue terminal 24b in the second pixelgroup 24 and emit blue light according to the driving current 30 fromthe blue terminal 24b.

Similarly, the strip of emissive orange material 45 includes multiplediscrete areas corresponding to the distinct terminals of the TFTbackplane 20, where each area in the orange strip 45 luminescesaccording to the driving currents 30 from each terminal. By way ofexample, the strip of orange emissive material 45 includes a first area46 situated to emit orange light according to a driving current 30conveyed from the green terminal 22g and also a second area 47 situatedto emit orange light according to a driving current 30 conveyed from thered terminal 22g. The patterned color filters 60 are arranged over thestrip of orange emissive material 45 to selectively transmit the redcomponents (70) and green components (70) of the emitted orange light50. A green filter 62 is arranged over the first area 46 and a redfilter is arranged over the second area 47. Similarly, a green filter 66and a red filter 68 are arranged over the orange emissive layer 45 atregions corresponding to the green terminal 24g and the red terminal24r, respectively, for the second pixel group 24. The red filters 62, 66selectively transmit the red color content from the electroluminescencespectrum of the orange emissive material 45 while the green filters 64,68 selectively transmit the green color content from theelectroluminescence spectrum of the orange emissive material 45. In someexamples, the red and green filters can be applied by a lithographicprocess.

The display panel 10 provides one exemplary arrangement for constructinga high resolution color display. For example, because the organicemissive materials can be deposited as substantially continuouselongated strips that span multiple pixel circuits, the dimensions ofthe individual emissive regions/areas (e.g., the areas 46, 47, etc.) arenot subject to several problems associated with other color displays.According to some other techniques, shadow masks made of thin metal(e.g., approximate thickness of 10 μm) with openings/holes arranged in apattern for each color are placed over a display substrate beforedepositing color-specific emissive materials. For example, a shadow maskwith openings at the positions of the red pixels is positioned over adisplay substrate with the openings aligned with the red pixels and ared emissive material was deposited; next a shadow mask with openings atthe positions of the blue pixels is positioned over the displaysubstrate and a blue emissive material was deposited, and so on foradditional colors. These techniques suffers from difficulty in aligningthe shadow masks with precision in two dimensions (along both height andwidth of the display panel), and also introduce practical limits on theminimum dimensions of the distinct emissive regions created via suchshadow masks.

At very high display resolutions, with pixel resolutions approaching (oreven exceeding) 300 pixels per inch (ppi), the pixel pitch (i.e., sizeof the active region for each pixel) is necessarily small, with typicaldimensions of each emissive region on the order of 10-20 micrometers,which is also the approximate thickness of the shadow mask itself. Insuch instances, directional deposition processes suffer from a shadowingproblem resulting in non-uniform thickness of the deposited organic filmacross the emissive region, even where the shadow mask is in directcontact with the display substrate. The non-uniform thickness resultsfrom the angle between the direction deposition source and the emissiveregion, resulting in some portion of the emissive region lacking aline-of-sight to the deposition source, due to an edge of the maskcasting a “shadow” blocking a portion of the emissive region from thedeposition source. The shadowed portion of the emissive region receivesrelatively little organic material in comparison to the non-shadowedportions of the emissive region. When the dimensions of the emissiveregion (i.e., the dimension of the openings in the shadow mask) aresignificantly larger than the dimensions of the thickness of the maskitself, this “shadowing” effect can largely be ignored. However, as thedimensions of the shadow mask approach the thickness of the shadow mask,the “shadowing” problem is exacerbated and can even result in an absenceof organic emissive material in a portion of the emissive region.

Some aspects of the present disclosure allow for a shadow mask to beformed with elongated openings that correspond to an area of the TFTbackplane 20 spanning more than one terminal. The elongated openings areless susceptible to shadowing effects because the boundaries of theresulting emissive regions are defined by edges of the shadow mask inone direction, rather than in both directions. In addition, the shadowmasks can be generally arranged to be carefully aligned along onedirection, with a greater alignment tolerance along the orientation ofthe elongated openings to facilitate rapid construction and assembly ofsuch displays.

Furthermore, aspects of the present disclosure provide for situatingcolor filters (e.g., the color filters 70) over one or more emissivelayers (e.g., the orange emissive material 45) to selectively transmitlight from the emissive material according to its color content.Advantageously, the present disclosure provides for displays thatinclude color filters over only a portion (“sub-set”) of the totalpixels such that light generated in the sub-set is partially blocked(via the filters), while light generated by other pixels is notfiltered. Using color filters to create color content is a wastefulenergy-consuming process, because the emissive regions are required togenerate light that does not contribute to the display content (i.e.,the light that is filtered/absorbed in the color filters representsenergy that does not contribute to the display content).

Thus, in contrast to a display that generates white light in theemissive regions for each pixel and then situates appropriate colorfilters over every pixel to selectively transmit light with the desiredcolor content, the arrangement in FIG. 1A (and other arrangementsdiscussed herein) allow for selective filtering of a subset of thepixels while other pixels emit light without being filtered. Sucharrangements increase the energy efficiency and/or operating lifetime ofsuch a device by decreasing the amount of light that is inefficientlyproduced (and absorbed in filters). In particular, the operatinglifetimes of the emissive regions and/or the circuit elements in the TFTbackplane can be extended by the present display arrangements bydecreasing the amount of electrical stress on the semi-conductivecomponents. Lowering the light production from each pixel decreases suchstresses by decreasing current density through the emissive layers andthe magnitude of the driving currents 30, and hence decreasing thevoltage stresses on the respective driving transistors.

Some embodiments of the present disclosure further provide formulti-color pixel groups formed to include a larger emissive region forblue light emission than for other colors. Blue emissive materials aremore sensitive to electrical degradation and typically degrade at ahigher rate than emissive materials for other colors. In some instances,the lifetimes of display devices due to electrical degradation of theemissive materials are controlled predominantly by the aging of the blueemissive materials which emit less light and/or require higher operatingvoltages over their lifetime to achieve a steady luminance. However, theaging of blue emissive materials can be reduced by decreasing thecurrent density through the emissive material. Thus, a tradeoff may bemade between display brightness (or emissivity, which correlates withcurrent density) and display aging, which occurs more rapidly at highercurrent densities. However, by increasing the relative area of the blueemissive region(s), the current density through the blue emissivematerial can be decreased while achieving substantially the same lightoutput from the blue material. In other words, a large blue emissiveregion allows the total current through the blue emissive material (andthus the total emissivity) to be the same as for a small blue emissiveregion, but the current density (which determines aging degradation)through the large region can be less than for the small region. Forexample, a multi-color pixel group can include red, green, and bluesub-pixels and the blue sub-pixel can include an emission region roughlytwice the size of the emission regions for each of the red and greensub-pixels. In such an arrangement, the current density through the bluesub-pixel is approximately half the value it would otherwise be if theblue emission region was the same size as the red and green emissionregions. As a result, the total aging degradation of such a display isgenerally less than displays with equal sized emissive regions for eachcolor, because the aging is not dominated by the degradation of the bluematerial.

FIG. 1B is a circuit diagram of a representative pixel circuit 100 inthe TFT backplane 20 for a pixel in an active matrix display including astorage capacitor 116 and a drive transistor 112 for conveying currentthrough the emission region according to charge on the storage capacitor116. The pixel circuit 100 is connected to a data line 122, a selectline 120, and first and second power supply lines 124, 126. A controller130 receives display data 138 (such as a video stream, etc.) indicatingan amount of luminance to be emitted from the pixel circuit 100. Thecontroller 130 operates a data driver 132 and an address driver 134 toprogram the pixel circuit 100 according to the received display data 138during a programming cycle, and allow the pixel circuit 100 to emitlight during an emission cycle. During the programming cycle for thepixel circuit 100, the address driver 134 sets the select line 120 toturn on the switch transistor 118 such that the data line 122 isconnected to the storage capacitor 116 via the switch transistor 118.Programming information is conveyed to the pixel circuit 100 to chargethe storage capacitor 116 via the data line 122. The storage capacitor116 is desirably arranged such that the drive transistor 112 is drivenduring the emission cycle according to a charge developed on the storagecapacitor 116 during the programming cycle. As shown in FIG. 1B, thestorage capacitor 116 can be connected between a gate terminal of thedrive transistor 112 and a stable voltage, such as a ground voltage,reference voltage, etc., sufficient to allow the storage capacitor 116to be charged according to the programming voltage. In some examples,the storage capacitor can be connected between the gate and/or sourceterminals of the drive transistor 112 such that the charge establishedon the storage capacitor 116 influences the conductance of the channelregion of the drive transistor 112. Thus, setting charging the voltageon the storage capacitor 116 thereby controls the current conveyedthrough the drive transistor 112 (and through the OLED 114) according tothe current-voltage characteristics of the drive transistor 112.

To initiate programming in the pixel circuit 100, the address driver 134operates a select line 120 to turn on a switch transistor 118. Forexample, the address driver 134 can set the select line 120 high to turnon the switch transistor 118 and thereby connect the pixel circuit tothe data line 122. The data line 122 is set to an appropriateprogramming voltage based on the display data 138 via the data driver132. The programming voltage can optionally be adjusted to account foraging degradation according to information in the memory 136. Theprogramming voltage on the data line 122 is conveyed, via the switchtransistor 118, to a storage capacitor 116 which is connected to thegate of a drive transistor 112. The storage capacitor 116 is connectedto a ground voltage at a terminal opposite the one connected to the gateof the drive transistor 112, to thereby situate the storage capacitor tobe charged according to the difference between the programming voltageand the ground voltage. However, it is specifically noted that thestorage capacitor 116 can also be connected to another stable voltagesuitable for allowing the storage capacitor 116 to be charged accordingto the programming voltage, such as, for example, a power supply voltageline (e.g., Vdd or Vss), a terminal of an OLED, or another terminalsufficient to prevent the storage capacitor 116 from floating duringprogramming. The drive transistor 112 is connected in series with alight emitting device 114, which can be an OLED, for example. The drivetransistor 112 and light emitting device 114 series is connected betweenfirst and second power supply lines Vdd 124 and Vss 126. The powersupply lines Vdd 124 and Vss 126 can provide fixed voltages or canoptionally be dynamically adjusted. For example, one or both of thepower supply lines 124, 126 can be adjusted to a value sufficient toreverse bias the light emitting device 114 during a programming cycle tothereby prevent emission from the light emitting device 114 during theprogramming cycle while the light emitting device 114 is beingprogrammed.

Thus, the pixel circuit 100 can be operated to emit light according toprogramming information by turning on the switch transistor 118, via theaddress driver 134, while a suitable programming voltage is establishedon the storage capacitor 116, via the data driver 132. The switchtransistor 118 is then turned off and the voltage on the storagecapacitor 116 controls gate-source voltage of the drive transistor bysetting the voltage on the gate of the drive transistor 112. Because theconductance of the channel region of the drive transistor 112 isinfluenced by its gate-source voltage (e.g., according to thecurrent-voltage characteristics of the drive transistor 112), thecurrent level through the drive transistor 112 is determined by thecharge on the storage capacitor 116. Furthermore, because the emissivityof the light emitting device 114 is established by the current flowingthrough the light emitting device 114, the light output from the pixelcircuit 100 is controlled according to the voltage on the storagecapacitor 116 during the driving cycle.

In some examples, the data driver 132 can set the data line 122 to aprogramming voltage, which allows the storage capacitor 116 to becharged according to the programming voltage. In other examples, thedata line 122 can optionally convey programming currents and the pixelcircuit 100 can be arranged to allow the storage capacitor 116 to becharge according to a voltage sufficient to maintain the programmingcurrent (or a current related to the programming current) through thedrive transistor 112 or another transistor such as a mirror transistor.

In some pixel architectures disclosed herein, the pixel circuits caninclude a stacked (“layered”) region forming one or more OLEDs andincluding more than one distinct emissive layer emitting light accordingto the current passing through each layer (such as in FIGS. 2A-2E). FIG.1C is a side view of an exemplary emissive region for a single pixelincluding stacked emissive layers and a color filter provided forillustrative purposes. The stacked region shown in FIG. 1C can beconsidered two OLEDs 171, 172 connected in series between a drivingelectrode 142 and a power supply line 166. The power supply line 166 canbe a transparent conductive material such as indium tin oxide (ITO)arranged on or near the encapsulation substrate 170. Each OLED 171, 172includes a cathode (the electron injection layers 144, 156 (EILs)) andan anode (the hole transport layer 152 and hole injection layer 164).

The driving electrode 142 is situated on a TFT backplane 140. Thedriving electrode 142 can be similar to the electrodes (“terminals”) ofthe TFT backplane 20 in FIG. 1A (e.g., the terminals 22r,g,b of thefirst pixel group). The driving electrode 142 is connected in serieswith a driving transistor for a pixel circuit within the TFT backplanesuch that current conveyed via the driving electrode 142 is controlledby the pixel circuit. For example, with reference to the pixel circuit100 of FIG. 1B, the driving electrode 142 can be connected to the drainterminal of the driving transistor 112. Referring again to FIG. 1C, theelectron injection layer (EIL) 144 is situated on the driving electrode142. The EIL 144 can generally be formed from a material including aconductive metal with a relatively high work function suitable forproviding free electrons to the OLEDs 171, 172, such as, for example,aluminum, gold, etc. The EIL 144 can also be a reflective material suchthat light emitted from one or both of the OLEDs 171, 172 is redirectedtoward the cap glass 170. The EIL 144 can also be considered the cathodeterminal of the OLED, and in some embodiments can be integrated with orotherwise combined with the driving electrode 142.

The first OLED 171 includes the EIL 144, a hole blocking layer 146(HBL), a first emissive layer 148 (EL-1), an electron blocking layer 150(EBL), and a hole transport layer 152 (HTL). The HBL 146 is situatedover the EIL 144 to prevent positively charged holes from reaching theEIL, where the holes would recombine with electrons outside of the firstemissive layer 148 (EL-1). The EL-1 148 is an organic film with amolecular structure suitable for emitting light 149 with a first colorin response to hole-electron recombination events occurring within EL-1148. The HBL 146 thus increases the efficiency of the first OLED 171 bymaximizing the number of recombination events (and thus emission events)that occur within EL-1 148. The EBL similarly increases the efficiencyof the first OLED 171 by blocking free electrons from traveling to theHTL 152, to thereby prevent the occurrence of inefficient (i.e.,non-light generating) recombination events outside the emissive layer148.

One or more intermediate layers 154 are provided between the HTL 152(which is also the anode of the first OLED 171) and the EIL 156 (whichis also the cathode of the second OLED 172). The intermediate layers 154can include substantially transparent and/or semi-transparent materialssuitable for conveying positive charged holes traveling from the secondOLED 172 to the HTL 152 of the first OLED 171. In some instances, theintermediate layers 154 can include tungsten trioxide, other nitridesand/or oxides, conductive metals, etc.

The second OLED 172 includes the EIL 156, an electron transport layer158 (ETL), a second emissive layer 160 (EL-2) a hole transport layer 162(HTL), and the HIL 164. The EIL 156 and HIL 164 define the cathode andanode of the second OLED 172, respectively. The EIL 156 is situated onthe intermediate layers 154 and releases free electrons through the ETL158 toward the emissive layer 160. In some examples, the EIL 156 and theETL 158 can be combined in a single layer. The EL-2 160 is anotherorganic film with a molecular structure suitable for emitting light 161with a second color in response to hole-electron recombination eventsoccurring within the EL-2 160. The HTL 162 and the HIL 164 are situatedon the EL-2160 for conveying positively charged holes to the EL-2 160.

Thus, current flowing through the OLEDs 171, 172 results in thegeneration of the first light 149 in the first emissive layer 148(EL-1), and the second light 161 from the second emissive layer 160(EL-2). The generated light 149, 161 is conveyed through the transparentand/or semi-transparent layers, including the power supply line 166formed of ITO toward the encapsulation glass 170. A color filter 168 isincluded on one side of the encapsulation glass 170 to allow thegenerated light 149, 161 to be selectively transmitted according to itscolor content. For example, the transmission spectrum of the colorfilter 168 can be such that the transmitted light is substantially redlight, green light, or blue light. In one example, the light 149 emittedfrom EL-1 148 can be blue light while the light 161 emitted from theEL-2 160 can be orange light such that the combined light 149, 161jointly includes a significant portion of the visible color spectrum andcan be considered white light. Thus, the color filter 168 canselectively transmit particular color contributions to the white light(e.g., red, green, blue color contributions). In another example, thelight 149 emitted from EL-1 148 can be red light while the light 161emitted from the EL-2 160 can be blue light and the color filter 168 canbe red or blue so as to selectively transmit light from one of theemissive layers (e.g., EL-1 148 or EL-2160) while largely blocking(“absorbing”) light from the other one.

The exemplary emissive region shown in FIG. 1C refers to a pixel circuitarranged to be “top-driven” with current flowing from the power supplyline 166, through the OLEDS 171, 172 toward the driving electrode 142which regulates the current level according to a series-connecteddriving transistor within the backplane 140. However, aspects of thepresent disclosure apply to bottom-driven pixel circuits arranged with adriving transistor connected in series with an anode of a layered OLEDdevice, and current flows from the driving electrode, through the OLED,and toward another power supply line. In bottom-driven pixelarrangements, it is also contemplated that the color filters (e.g., thecolor filters 60 in FIG. 1A) can be applied to the display substrate(e.g., via a lithographic process).

In the following figures and accompanying descriptions, several examplesof arrangements (“architectures”) for arranging a multi-color pixelgroup with emissive layers that span multiple terminals and with colorfilters arranged to filter light from a subset of the pixels in eacharrangement. It is specifically contemplated that the pixel groupsdisclosed herein are can be patterned across a display panel andarranged in rows and columns to allow for independently controlled colorcontent across a display panel to thereby generate color images and/orvideo. In addition, it is specifically noted that the arrangements andarchitectures described herein include layouts for emissive regions,driving terminals, and/or color filters, and can be applied to a varietyof pixel circuits employing a variety of different programming anddriving schemes. In addition, it is specifically understood thatadditional layers and/or materials can be included between and/or aroundemissive layers, such as described by way of example in FIG. 1C.

Furthermore, for clarity and consistency of the present disclosure, thearrangements and architectures included herein are described astop-driven pixel circuits situated on a TFT backplane substrateincluding a pattern of separately controllable driving terminals.However, it is noted that the present disclosure applied to other pixelcircuit layouts including bottom-driven arrangements.

FIG. 2A is a top view of a layout 200 for an RGBW multi-color pixelgroup formed with a substantially continuous strip of blue emissivematerial 220 on a blue driving terminal 206 and a white driving terminal208. The RGBW pixel group includes a red pixel R1 defined by the reddriving terminal 202, a green pixel G1 defined by a green drivingterminal 204, and blue and white pixels (B1 and W1) defined by a bluedriving terminal 206 and a white driving terminal 208, respectively. Anorange emissive material 222 is distributed in a layer covering all theterminals in the RGBW group. Thus, orange light is produced from theemissive regions for the red and green pixels (R1 and G1) via the orangeemissive layer 222. A red filter 212 is situated over R1 to selectivelytransmit the red content in the emitted orange light, while a greencolor filter 214 is situated over G1 to selectively transmit the greencontent in the emitted orange light. A blue filter 216 is situated overB1 to selectively transmit the blue light (emitted via the blue emissivestrip 220) while blocking light from the orange layer 222. The whitepixel emits substantially all the substantially white light from thecombined stack of orange light (via the orange layer 222) and blue light(from the blue layer 220).

In some embodiments of the layout 200, the red, green, blue, and whitepixels of the RGBW pixel group each include emissive regions with asimilar size and/or area. Generally, the size and/or shape of theemissive region of the pixels in the layout 200 are defined by the sizeof the corresponding driving terminals (e.g., the driving terminals 202,204, 206, 208). In some cases the driving terminals 202-208 can each beapproximately the same size. For example, the RGBW pixel group can bearranged as a square divided in quadrants and each quadrant can includeone of the driving terminals 202-208. Furthermore, each of the drivingterminals 202-208 can be a square or rounded square with similar heightsand widths, and the color filters 212-216 can be arranged with similardimensions to the driving terminals 202-206 so as to filter light fromthe respective emissive regions of the pixels R1, G1, B1.

FIG. 2B is an aspect view of the RGBW multi-color pixel group layout 200with the strip of blue emissive material 220 formed over a layer oforange emissive material 222. In some embodiments, a display panelformed with pattern of pixels arranged according to the layout 200 canbe formed by depositing (“developing”) the orange emissive layer 222 ina substantially uniform, continuous layer across the display panel.Following the development of the orange layer 222, any desiredintermediate layers can be situated, and a shadow mask can be alignedwith an elongated opening over the blue and white pixels B1, W1. Forexample, the elongated opening can extend across multiple such pixelgroups in a continuous line of adjacent alternating blue and whitepixels in multiple RGBW pixel groups. The blue emissive layer 220 can bedeposited in the desired region while the shadow mask blocks the blueemissive material from the red and green pixels R1, G1. Additionallayers and/or conductive power supply lines can be arranged on theemissive regions of the display panel and the color filters can then bearranged such that the desired colors are transmitted from each of thered, green, blue, and white pixels in each group. As previously noted, alithographic process can be employed to apply appropriatecolor-selective filtering materials (e.g., the color filters 212, 214,216) to the display substrate and/or encapsulation substrate.

FIG. 2C is an aspect view of the RGBW multi-color pixel group layout 200with the layer of orange emissive material 222 formed over the strip ofblue emissive material 220. In an exemplary process to construct adisplay panel with RGBW pixel group layout 200, a shadow mask issituated with an elongated opening over blue and white terminals formultiple pixels and the blue emissive material 220 is deposited in asubstantially continuous layer in the region defined by the shadow maskopening. Intermediate layers are situated as desired and the entiredisplay panel is coated with a substantially continuous layer of theorange emissive material 222. The color filters 212, 214, 216 arearranged over the red, green, and blue pixels (R1, G1, B1) toselectively transmit red, green, and blue light. Thus, the layout 200 ofFIG. 2A can be achieved without regard to the order of the orange andblue emissive materials 222, 220 in the stacked emissive regions of theblue pixel B1 and white pixel W1.

FIG. 2D is a top view of an alternative configuration of the RGBWmulti-color pixel group layout 240 with a red pixel R2 and a green pixelG2 each having elongated emissive regions. The emissive materials 220,222 in the RGBW pixel group 240 are arranged similarly to the emissivelayers in the RGBW pixel group 200 in FIGS. 2A-2C, with the orangeemissive material 222 distributed in a substantially continuous layeracross all pixels in the group, and a strip of blue emissive material220 over the blue terminal 206 and the white terminal 208. Thus, theblue pixel B2 and the white pixel W2 are arranged similarly to thepixels B1 and W1 in the pixel group layout 200. However, the arrangementof the red driving terminal 232 and the green driving terminal 234differs from the RGBW pixel group layout 200. As shown in FIG. 2D, theRGBW pixel group layout 240 is arranged roughly as a square withapproximately equal width and height. The driving terminals for the redand green pixels 232, 234 are each arranged as rectangles with a lengthspanning (or nearly spanning) the height dimension of the RGBW pixelgroup 240. The width of the terminals 232, 234 is approximately onequarter the width of the RGBW pixel group layout 240. In someembodiments, the elongated driving terminals 232, 234 can haveapproximately the same surface area as the terminals 202, 204 arrangedapproximately as squares in quadrants of the square-shaped multi-colorpixel group layout 200.

A red color filter 242 is situated to selectively transmit the red lightfrom the orange emissive layer 222 receiving current from the reddriving terminal 232. Similarly, a green color filter 244 is situated toselectively transmit the green light from the orange emissive layer 222receiving current from the green driving terminal 232. The dimensions,size, and/or shape of the color filters 242, 244 can be selected tocorrespond to the dimensions, size, and/or shape of the respectivedriving terminals 232, 234. In some examples, the color filters 242, 244can be larger than their corresponding driving terminals 232, 234 toallow the color filters 242, 244 to completely overlap the emissiveregions of the pixels R2, G2, while allowing for some alignmenttolerance in positioning the color filters 242, 244 with respect to thepixels R2, G2 (and their respective driving terminals 232, 234).

While the present disclosure includes two specific arrangements for thered and green pixels with R1, G1 approximately arranged as squares inquadrants of the layout 200 (FIG. 2A) and R2, G2 approximately arrangedas adjacent rectangles extending the length of the pixel group layout240 (FIG. 2D), the present disclosure extends to other arrangements.Generally, the driving terminals for the red and green pixels can bearranged to divide a portion of a multi-color pixel group that includesa layer of orange emissive material into distinct areas that areseparately programmed and driven to emit light. Red and green colorfilters are situated in regions corresponding to the driving terminalssuch that red light is selectively transmitted from one pixel and greenlight is selectively transmitted from the other pixel, and the shape ofthe color filters can be a shape that is based on the shape of thedriving terminals. The red and green color filters are situated over theportions of the orange emissive material driven by the independentlyprogrammed driving terminals such that the transmitted light from eachpixel circuit is substantially red and green, respectively.

FIG. 2E is a top view of a layout for an RGB multi-color pixel grouplayout 260 including emissive layers 220, 222 arranged similarly to thelayouts of FIGS. 2A and 2D. The arrangement of the RGB pixel group 260includes red, green, and blue pixels (R3, G3, and B3). The red pixel R3and green pixel G3 pixels are arranged similarly to the red and greenpixels R1, G1 in the RGBW layout 200, with the red and green pixels eacharranged as a separately programmed quadrant of the square-shaped pixelgroup layout 260. The blue pixel B3 includes a blue driving terminal 266that conveys current through the stacked emissive region including thestrip of blue emissive material 220 and the orange emissive material222. A blue color filter 276 is situated to cover the blue pixel B3 suchthat the light from the blue emissive material 220 is transmitted whilethe orange light from the orange emissive material 222 is blocked. Wherea display panel is formed by patterning the layout 260 across a panel,adjacent blue pixels from multiple RGB pixel groups can be arranged in acontinuous column (or row) of the panel, and the blue color filteringmaterial can be applied to the strip of blue emissive material 220across its entire length (or nearly entire length).

The blue driving terminal 266 spans roughly one-half of thesquare-shaped pixel group layout 260. The blue pixel B3 has a largeremissive region (as measured by area) than the emissive regions ofeither the red or green pixels R3, G3. Thus, blue light is emitted fromapproximately one-half of the pixel group, rather than approximatelyone-fourth, as in the pixel group layouts 200, 240 of FIGS. 2A-2D.Furthermore, a display panel patterned according to the layout 260,transmits blue light from roughly half (or nearly half) of the displayarea of the panel, similar to the display panel 10 of FIG. 1A. Similarto the discussion of the relative sizes of the blue pixel areas inconnection with FIG. 1A, providing a layout (e.g., the layout 260) withan increased relative size of the blue pixel allows for decreasing thecurrent density through the strip of blue emissive material 220 withoutloss of display brightness and thereby allows for decreasing the agingdegradation of the display panel.

FIG. 3A is a top view of a layout 300 for an RGB multi-color pixel groupformed from alternating strips of orange emissive material 322 and blueemissive material 320 and with a blue sub-pixel B4 enlarged relative tored and green sub-pixels (R4, G4). The red pixel R4 includes a reddriving terminal 302; the green pixel G4 includes a green drivingterminal 304; and the blue pixel B4 includes a blue driving terminal306. The arrangement of the driving terminals 302-306 in the RGB pixelgroup 300 of FIG. 3A is similar to the driving terminal arrangement inthe layout 260 of FIG. 3A. Generally, the RGB pixel group of FIG. 3A isarranged as a square with the red pixel R4 and green pixel G4 eachoccupying roughly one quadrant of the square, and the blue pixel B4occupying roughly the remaining half of the square. The strip of orangeemissive material 322 is a substantially continuous layer that coversthe driving terminals 312, 314 of the red and green pixels (R4, G4). Ared color filter 312 and a green color filter 314 are situated over theportions of the orange emissive material 322 driven by the red drivingterminal 302 and the green driving terminal 304, respectively. Thus, theRGB pixel group 300 transmits red light from the red pixel R4, greenlight from the green pixel G4, and unfiltered blue light is emitted fromthe blue pixel B4. As described previously, the relatively large size ofthe blue pixel B4 in comparison to the red and green pixels (R4, G4)reduces degradation associated with the blue emissive material 320 byreducing the current density through the blue emissive material. Thelayout 300 of the RGB pixel group in FIG. 3A is similar to the layoutsof the multi-color pixel groups 22, 24 of FIG. 1A.

FIG. 3B is a top view of a layout 340 for an RGB multi-color pixel groupsimilar to the layout 300 in FIG. 3A, but where the red and greensub-pixels (R5, G5) have elongated emissive regions. The RGB pixel groupis roughly arranged as a square, and the blue pixel B5 occupies roughlyhalf of the square, similar to the blue pixel B4 in FIG. 3A. However, inthe layout 340, a red driving terminal 332 and a green driving terminal334 are arranged as adjacent rectangles that jointly span roughly halfof the square-shaped pixel group. The rectangular red and green drivingterminals 332, 334 can have lengths roughly spanning the height of thesquare-shaped pixel group, and with widths roughly spanning one-quarterthe width of the square-shaped pixel group. A red color filter 342 and agreen color filter 334 are situated over the portions of the orangeemissive material 322 driven by the red driving terminal 332 and thegreen driving terminal 334, respectively. In some examples, the layout340 is preferred over the layout 300 of FIG. 3A, because the layout 340situates all three pixels R5, G5, B5 of the multi-color pixel group in asingle row, rather that splitting the red and green pixels across tworows (pixels R4, G4 of FIG. 3A). In some embodiments, arranging all thepixels R5, G5, B5 in a single row as in the layout 340 can allow forless redundancy and more uniform spacing in selection, addressing,programming, and/or power supply lines in the TFT backplane.

In comparison to the arrangements in FIGS. 2A-2E, the RGB pixel grouplayouts 300, 340 of FIGS. 3A-3B do not include blue color filters,because the blue pixels B4, B5 include only blue emissive material andare not stacked emissive regions also including orange emissivematerial. Display panels formed by patterning either of the layouts 300,340 can thus be operated at a higher energy efficiency than the displaysarranged according to the layouts 200, 240, 260 of FIGS. 2A-2E, becauseless light is filtered (i.e., wasted).

FIG. 4A is another top view of a layout 400 for RGB multi-color pixelgroups formed from alternating strips of orange emissive material 420,424 and blue emissive material 422 and with adjacent blue pixels beingassociated with red and green sub-pixels in alternating upper and lowerrows. Thus, a first RGB pixel group includes a red pixel R6, a greenpixel G6, and a blue pixel B6. A second RGB pixel group includes a redpixel R7, a green pixel G7, and a blue pixel B7. The red pixel R6 andthe green pixel G6 include a common, substantially continuous strip oforange emissive material 420 that spans respective driving terminals402, 404 for the red and green pixels R6, G6. A red filter 412selectively transmits red light from the red pixel R6 while a greenfilter 414 selectively transmits green light from the green pixel G6.Similarly, the red pixel R7 and the green pixel G7 include a common,substantially continuous strip of orange emissive material 424 thatspans respective driving terminals 432, 434 for the red and green pixelsR7, G7. A red filter 442 selectively transmits red light from the redpixel R7 while a green filter 444 selectively transmits green light fromthe green pixel G7. The blue pixels B6, B7 include a common,substantially continuous strip of blue emissive material 422 that spansrespective driving terminals 406, 436 for the blue pixels B6, B7. Theblue pixels B6, B7 are situated between the adjacent red and greenpixels R6, G6 in the first RGB pixel group and the adjacent red andgreen pixels R7, G7 in the second RGB pixel group.

The substantially continuous strips of orange emissive material 420 canbe developed by placing a shadow mask with an elongated opening alignedover an area including the driving terminals 402, 404 for the red andgreen pixels R6, G6 and depositing the orange emissive material 420 toform the substantially continuous strip with roughly uniform thicknesswhile preventing the orange emissive material 420 from reaching theemissive regions for the blue pixels B6, B7. The elongated opening ofthe shadow mask (and thus the substantially continuous layer 420) canoptionally extend to span multiple alternating adjacent red and greenpixels from additional RGB pixel groups (not shown). Further, the shadowmask can be arranged with an additional elongated opening aligned overan area including the driving terminals 432, 434 for the red and greenpixels R7, G7. Alternatively, the strip of orange emissive material 424can be developed via a separate shadow mask.

Before and/or after the strips of orange emissive materials 420, 424,another shadow mask is placed over the display panel with an elongatedopening in the shadow mask aligned over an area including the drivingterminals 406, 436 of the blue pixels B6, B7. The elongated opening inthe shadow mask can extend to include emissive regions for additionalblue pixels in the display panel such that the strip of blue emissivematerial 422 spans an area including multiple blue pixels and has asubstantially constant thickness across the area. The shadow mask usedto develop the strip of blue emissive material 422 can optionally be thesame as the one used for the red and green pixels, but repositioned toalign its elongated opening with the blue pixels B6, B7 while coveringthe red and green pixels R6, G6, R7, G7.

The red and green pixels R6, G6 of the first RGB pixel group can beadjacent pixels in a first row of a display panel. The blue pixels B6,B7 of the first and second RGB pixel groups can be adjacent pixels in asecond row immediately above or below the red and green pixels R6, G6 ofthe first group. The red and green pixels R7, G7 of the second RGB pixelgroup can be adjacent pixels in a third row immediately adjacent thesecond row. Thus, the first and second pixel groups can span two columnsand three rows of a display panel. Alternatively, the layout can berotated by 90 degrees such that the two pixel groups include threecolumns and two rows.

In some examples of the layout 400, each of the pixels R6-B6 and R7-B7can have an approximately equal area and have approximately equallysized driving terminals. For example, the two pixel groups can bearranged as a rectangle divided into six approximately equally-sizedsquares arranged in a 2 by 3 array, with the upper two squares occupiedby the red and green pixels R6, G6, the middle two squares occupied bythe blue pixels B6, B7 and the lower two squares occupied by the red andgreen pixels R7, G7.

FIG. 4B is a top view of a layout 450 for an RGB multi-color pixel groupsimilar to the layout of FIG. 4A, but where the blue pixels B6′, B7′ ineach RGB multi-color pixel group have a larger area than either the redor green pixels R6, G6, R7, G7. As shown in the layout 450, a blueemissive layer 452 is provided in a substantially continuous strip thatincludes the blue pixels B6′, B7′. The blue pixels B6′, B7′ are drivenvia driving terminals 456, 458 that are separately programmed and drivento cause the blue emissive layer to emit light according toindependently determined luminance values. Thus, the driving terminals456, 458 define respective portions of the substantially continuousstrip of blue emissive material 452 included in the blue pixel B6′ forthe first RGB pixel group and the blue pixel B7′ for the second RGBpixel group, respectively.

The red and green pixels R6, G6, R7, G7 are each roughly as squares ofdimension d1. The blue pixels B6′, B7′ are each arranged as rectangleswith a width approximately given by the widths of the red and greenpixels R6, G6, R7, G7 (e.g., d1) and a height given by d2, which islarger than d1. Thus, the areas of the two blue pixels B6′, B7′ are eachlarger than the areas of the red and green pixels R6, G6, R7, G7. Thewidth of the strip of blue emissive material 452 is larger than d2 toallow for an alignment tolerance while still achieving nearly completecoverage of the driving terminals 456, 458 of the blue pixels B6′, B7′.In an example, d2 can be approximately twice d1 such that the emissiveregion of each of the blue pixels B6′, B7′ is roughly twice the area ofthe emissive regions of each of the red and green pixels R6, G6, R7, G7.

When patterning a display panel according to the layout 450, the red andgreen pixels R6, G6 can be immediately below another pair of red andgreen pixels for another RGB pixel group (not shown), and the orangeemissive layer 420 can extend, along the width of the strip, to coverthe other pair of red and green pixels. In some instances, the widthdimensions of the alternating strips of orange and blue emissivematerial deposited on a display panel can be approximately equal, evenwhere the blue pixels (e.g., B6′, B7′) are each roughly twice the areaof each of the red and green pixels R6, G6, R7, G7, because the stripsof orange emissive material (e.g., 420, 424) cover a region of red andgreen pixels that is two pixels wide (e.g., approximately twice thedimension d1, plus an alignment margin). The region of red and greenpixels can be two rows of checkered red and green pixels, alternatingadjacent pairs of red and green pixels, or some other regularlyrepeating pattern of red and green pixels.

Furthermore, while the blue pixels B6′, B7′ are shown as extended alonga vertical dimension d2, such that the blue pixels B6′, B7′ are includedin a single column, the present disclosure also applies to enlarged bluepixels that are rotated with an extended dimension roughly spanning apair of red and green pixels. For example, the layout 450 can bemodified with the blue pixels B6′, B7′ pixels each rotated 90 degreesclockwise about an axis located centrally between the two. Thus, thefirst blue pixel B6′ can be situated immediately below the red and greenpixels R6, G6 in the first RGB pixel group, and the blue pixel B7′ canbe situated immediately above the red and green pixels R7, G7 in thesecond RGB pixel group.

FIG. 4C is a top view of a layout 460 for an RGB multi-color pixel groupsimilar to the layout of FIG. 4B but where adjacent multi-color pixelgroups share a common unitary blue pixel B6/B7. In the layout 460, thecommon unitary blue pixel B6/B7 can occupy roughly the same area as thecombination of the blue pixels B6′, B7′ in the layout 450 of FIG. 4B.The common unitary blue pixel B6/B7 includes a single driving terminal466 that is programmed according to a luminance value based onprogramming information for the first and second multi-color pixelgroups. Thus, in the layout 460, adjacent multi-color pixel groups sharea single blue pixel (e.g., the blue pixel B6/B7), while stillmaintaining the distinct red and green pixels R6, G6, R7, G7. The commonblue pixel B6/B7 is driven to emit blue light with a luminance that isbased on incoming blue content of a displayed image from the regions ofthe first and second pixel group. In some examples, the blue pixel B6/B7can be driven according to an average blue luminance contribution fromtwo adjacent RGB pixels corresponding to the first and second RGB pixelgroups in the layout 460.

FIG. 4D is a top view of a layout 470 for an RGB multi-color pixel groupsimilar to the layout 450 of FIG. 4B with the red and green sub-pixelshaving elongated emissive regions. The alternating strips of orangeemissive material 420, 424 and blue emissive material 452 are situatedas in the layout 450 shown in FIG. 4B. However, the strips of orangeemissive material 420, 424 are divided into red and green pixels (e.g.,the pixels R8, G8, R9, G9) by rectangular driving terminals 482, 484,493, 495 elongated along the extended direction of the strip of orangeemissive material 420, 424. The rectangular driving terminals 482, 484,493, 495 are situated to include two adjacent rows of the red and greenpixels in the strip of orange emissive material 420, 424. Red colorfilters 472, 474 and green color filters 492, 494 are situated toselectively transmit the red content, and green content, respectively,emitted in the strips of orange emissive material 420, 424.

Thus, the rectangular driving terminals 482, 484, 493, 495 are arrangedin two adjacent rows of red and green pairs for each RGB pixel group. Bycontrast, the layout 450 includes alternating red and green squaredriving terminals in a single row. The red and green pixels R8, G8, R9,G9 have a width spanning the two adjacent blue pixels B8, B9 and aheight dimension sufficiently small to allow the strip of orangeemissive material 420 to overlap both red and green driving terminals482, 484. In some examples, the red and green pixels R8, G8, R9, G9 inthe layout 470 have a height roughly half that of the red and greenpixels R6, G6, R7, G7 in the layout 450 of FIG. 4B, and have a widthroughly twice that of the red and green pixels in the layout 450.

FIG. 5 is a top view of a layout 500 for an RGB multi-color pixel groupformed from parallel strips of red and green emissive materials 520, 522overlapped with perpendicularly aligned strips of blue emissive material524. The layout 500 includes a first RGB pixel group including a redpixel R10, a green pixel G10, and a blue pixel B10. The layout 500 alsoincludes a second RGB pixel group including a red pixel R11, a greenpixel G11, and a blue pixel B11. It is noted that the arrangement of thedriving terminals in the layout 500 can be the same or similar as thearrangement of driving terminals in the layout 400 of FIG. 4A.

In reference to the layout 500 of FIG. 5, the red pixel R10 is driven bya driving terminal 502 to convey current through the red emissivematerial 520. The green pixel G10 is driven by a driving terminal 504 toconvey current through the green emissive material 522. The blue pixelB10 is driven by a driving terminal 506 to convey current through thered emissive material 520 and the blue emissive material 524, which arearranged in a stacked configuration. The blue pixel B11 is driven by adriving terminal 516 to convey current through the green emissivematerial 522 and the blue emissive material 524, which are arranged in astacked configuration.

Generally, the strip of blue emissive material 524 can be situated overor under the red and green emissive materials 520, 522. However, bothstrips of the red and green emissive material 520, 522 areadvantageously on the same side (e.g., over or under) of the blueemissive material 524 to provide efficiency in constructing a displaypanel including the pattern 500. For example, a process can begin withdepositing the strip of red emissive material 520 (or a pattern of suchstrips) on a display substrate via a shadow mask having an elongatedopening aligned to include the emissive region of the red pixels R10,R11 and the blue pixel B10. The shadow mask can then be translated byroughly the dimension of a single pixel such that the elongated openingis aligned to include the emissive region of the green pixels G10, G11and the blue pixel B11, and the green emissive material 522 can bedeposited. To develop the substantially continuous strip of blueemissive material 524 oriented perpendicularly to the two red and greenstrips 520, 522, the same shadow mask can be rotated about 90 degrees,or another shadow mask can be positioned over the display substrate withan elongated opening aligned to include the emissive regions of the bluepixels B10, B11, and the blue emissive material 524 can be deposited.Because the translation of the shadow mask while maintaining a parallelorientation of the shadow mask's elongated opening is generally a fasterprocess than either rotating a shadow mask or positioning a differentshadow mask, the substantially continuous strips of red and greenemissive material 520, 522 are desirably deposited consecutively

A blue color filter 508 is situated to selectively transmit the bluecontent from the light emitted in the blue pixels B10, B11. In someexamples, the blue color filter 508 can be applied to continuously spana row of adjacent blue pixels including the blue pixels B10, B11. Inreference to the layout 500 of FIG. 5, it is noted that the only pixelsin the RGB pixel groups that are filtered are the blue pixels B10, B11,while the red and green pixels emit unfiltered light. The net luminanceof a typical display is dominantly provided by red and green colorcontributions, with blue light contributions providing much less lightoverall (perhaps as little as 3% in total luminance contributions in atypical display). Furthermore, the human retina is generally moresensitive (“responsive”) to red and green light than blue light and sobright images can be perceived while relying primarily on red and greencolor contributions to a given image. Thus, by filtering the bluepixels, rather than the red or green pixels, there is relatively littlelight that is wastefully generated only to be blocked by a color filter.Accordingly, the layout 500 provides for a relatively high degree ofenergy efficiency by filtering only the blue light contributions to thetotal luminance and emitting the red and green contributions to thetotal luminance without significant color filters to partially block thelight generated in those regions.

FIG. 6A is a top view of a layout 600 for RGB multi-color pixel groupsformed from parallel strips of red and green emissive materials 620, 622overlapped with perpendicularly aligned strips of blue emissive material625, 626 and with blue pixels B12, B13 enlarged relative to red andgreen sub-pixels R12, G12, R13, G13. FIG. 6B is an aspect view of theRGB multi-color pixel groups of FIG. 6A showing alignment of the layersof emissive material 620, 622, 624, 626 and color filters 608, 618 withrespect to a TFT backplane 630.

In the layout 600, a first RGB pixel group includes a red pixel R12, agreen pixel G12, and a blue pixel B12, and a second RGB pixel groupincludes a red pixel R13, a green pixel G13, and a blue pixel G13.Substantially continuous parallel strips of red emissive material 620and green emissive material 622 are arranged over the red pixels R12,R13 and green pixels G12, G13, respectively. The strips of red and greenemissive material 620, 622 also extend over a portion of the blue pixelsB12, B13. A substantially continuous strip of blue emissive material 625is oriented perpendicularly to the red and green strips 620, 622 andcovers the blue pixel B12. Another substantially continuous strip ofblue emissive material 626 is also oriented perpendicularly to the redand green strips 620, 622 and covers the blue pixel B13.

In the first RGB pixel group, the red pixel R12 includes a drivingterminal 602 for conveying current through the red emissive material620; the green pixel G12 includes a driving terminal 604 for conveyingcurrent through the green emissive material 622; and the blue pixel B12includes a driving terminal 606 for conveying current through the blueemissive material 625, the red emissive material 620, and the greenemissive material 622. A blue color filter 608 is situated toselectively transmit the blue light from the blue pixel B12 (e.g., byblocking the red and green light from the portions of the red and greenemissive materials overlapping the driving terminal 606). In the secondRGB pixel group, the red pixel R13 includes a driving terminal 612 forconveying current through the red emissive material 620; the green pixelG13 includes a driving terminal 614 for conveying current through thegreen emissive material 622; and the blue pixel B13 includes a drivingterminal 616 for conveying current through the blue emissive material625, the red emissive material 620, and the green emissive material 622.A blue color filter 608 is situated to selectively transmit the bluelight from the blue pixel B12 (e.g., by blocking the red and green lightfrom the portions of the red and green emissive materials overlappingthe driving terminal 606). As shown in FIGS. 6A-6B, the first RGB pixelgroup is roughly arranged as a square with the red and green pixels R12,G12 each occupying roughly one quadrant of the square and the blue pixelB12 approximately occupying the remaining half of the square. Similarly,the second RGB pixel group is roughly arranged as a square with the redand green pixels R13, G13 each occupying roughly one quadrant of thesquare and the blue pixel B13 approximately occupying the remaining halfof the square.

While the arrangement of the overlapping emissive regions in the layout600 is distinct from other layouts disclosed herein, it is noted thatthe arrangement of the driving terminals in the layout 600 of FIGS.6A-6B can be the same or similar to the arrangement of the drivingterminals in the layout 300 of FIG. 3A. Thus, the ratio of areas of thedisplay panel occupied by red, green, and blue pixels in a display panelpatterned according to the layout 600 can be the same or similar to adisplay panel patterned according to either the layout 300. Furthermore,the discussions above regarding the relative size (“area”) of the blueemissive region with respect to the red and green emissive regions inthe layout 300 for the RGB pixel group so as to mitigate the agingdegradation of the display also applies to the layout 600 of FIGS.6A-6B.

High resolution display panels and/or display systems can be constructedaccording to any of the layouts disclosed herein by patterning thelayouts across a display panel to create a regularly repeating patternof evenly distributed red, green, blue, and/or white emitting pixelsthat are separately programmed.

Generally, the physical dimensions of the multi-color pixel groupsdescribed herein can be selected for a particular implementation onceconstraints for total display size, and display resolution are known. Byway of example, a display size 3 inches wide by 1.69 inches high with aresolution of 1920 by 1080 pixels, each multi-color pixel group isroughly situated in an area given by a square with sides roughly 0.0016inches (or roughly 40 μm). For the same display size with a resolutionof 1280 by 720 pixels, each multi-color pixel group is roughly situatedin an area given by a square with sides roughly 0.0023 inches (orroughly 60 μm). Thus, achieving such displays generally require pixelpitch of approximately 40-80 μm, which corresponds to pixel densitiesapproaching, or even exceeding, 300 pixels per inch.

The exemplary layouts disclosed herein are described as oriented alongrows and/or columns for purposes of clarity in referring to arrangingthe layouts on a display panel. However, it is specifically understoodthat any of the layouts described herein can be rotated by 90 degreesand references to rows/columns described herein therefore apply equallyto similar descriptions referring to columns/rows of a display panel.

Circuits disclosed herein generally refer to circuit components beingconnected or coupled to one another. In many instances, the connectionsreferred to are made via direct connections, i.e., with no circuitelements between the connection points other than conductive lines.Although not always explicitly mentioned, such connections can be madeby conductive channels defined on substrates of a display panel such asby conductive transparent oxides deposited between the variousconnection points. Indium tin oxide is one such conductive transparentoxide. In some instances, the components that are coupled and/orconnected may be coupled via capacitive coupling between the points ofconnection, such that the points of connection are connected in seriesthrough a capacitive element. While not directly connected, suchcapacitively coupled connections still allow the points of connection toinfluence one another via changes in voltage which are reflected at theother point of connection via the capacitive coupling effects andwithout a DC bias.

Furthermore, in some instances, the various connections and couplingsdescribed herein can be achieved through non-direct connections, withanother circuit element between the two points of connection. Generally,the one or more circuit element disposed between the points ofconnection can be a diode, a resistor, a transistor, a switch, etc.Where connections are non-direct, the voltage and/or current between thetwo points of connection are sufficiently related, via the connectingcircuit elements, to be related such that the two points of connectioncan influence each another (via voltage changes, current changes, etc.)while still achieving substantially the same functions as describedherein. In some examples, voltages and/or current levels may be adjustedto account for additional circuit elements providing non-directconnections, as can be appreciated by individuals skilled in the art ofcircuit design.

Any of the circuits disclosed herein can be fabricated according to manydifferent fabrication technologies, including for example, poly-silicon,amorphous silicon, organic semiconductor, metal oxide, and conventionalCMOS. Any of the circuits disclosed herein can be modified by theircomplementary circuit architecture counterpart (e.g., n-type transistorscan be converted to p-type transistors and vice versa).

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationscan be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A high resolution display panel comprising: adisplay substrate including at least first and second substantiallycontinuous emissive layers that are common to, the lengths of saidlayers spanning multiple pixels along the lengths of said layers, saidfirst and second emissive layers having different colors, each of saidpixels including a first driving terminal aligned with a segment of saidfirst emissive layer to form a first sub-pixel, the first and secondemissive layers overlapping in an area defined by the first drivingterminal, the first sub-pixel producing light of a first color inresponse to current being conveyed through said first and secondemissive layer layers from said first driving terminal, second and thirddriving terminals aligned with different portions of said secondemissive layer and located on a first side of said second emissive layerto form second and third sub-pixels producing light of a second color inresponse to current being conveyed through said second emissive layerfrom said second and third driving terminals, and first and second colorfilters aligned with said second and third driving terminals and locatedon the opposite side of said second emissive layer from said second andthird driving terminals to produce transmit light of third and fourthcolors from said second and third sub-pixels, and a third color filteraligned with said first driving terminal and located on an opposite sideof said first and second emissive layers from said first drivingterminal to transmit light of a fifth color from said first sub-pixel.2. The high resolution display panel according to claim 1, wherein saidemissive layers, and said color filters, are arranged such that the afirst fundamental color, a second fundamental color, and a thirdfundamental color are emitted from the display panel via said first,second and third sub-pixels arranged in a regularly repeating patternacross the display panel.
 3. The high resolution display panel accordingto claim 2, wherein said first emissive layer emits blue light, saidsecond emissive layer emits orange light, and said first and secondcolor filters transmit red and green light.
 4. The high resolutiondisplay panel according to claim 3, wherein said first driving terminaloccupies a larger surface area of the display panel than said second andthird driving terminals.
 5. The high resolution display panel accordingto claim 4, wherein the third color filter transmits blue light.
 6. Thehigh resolution display panel according to claim 1, wherein the thirdcolor filter transmits blue light.
 7. The high resolution display panelaccording to claim 6, wherein said first driving terminal occupies alarger surface area of the display panel than said second and thirddriving terminals.
 8. The high resolution display panel according toclaim 1, wherein each pixel further comprises: a fourth driving terminalaligned with portions of said first emissive layer different fromportions of said first emissive layer aligned with said first terminals,to form a fourth sub-pixel producing light of the first color inresponse to current being conveyed through said first emissive layer andthrough said second emissive layer from said first driving terminal,wherein the first and second emissive layers overlap in an area definedby the fourth driving terminal.
 9. The high resolution display panelaccording to claim 8, wherein the first color is white resulting fromthe blue light emitted from the first emissive layer and the orangelight emitted from the second emissive layer.
 10. The high resolutiondisplay panel according to claim 8, wherein the fourth sub-pixel is suchthat said light of the first color, white, is transmitted from said areadefined by the fourth driving terminal substantially unfiltered.